1. Field of the Invention
The present invention relates to a PC card capable of being plugged into a computer system, where the PC card is capable of switching between a 16-bit operation mode and a 32-bit operation mode. More particularly, the invention relates to a PC card capable of automatically switching operation modes upon being plugged into a card slot of a computer system.
2. Description of the Related Art
A PC card is a peripheral device developed for expanding capabilities of a personal computer (PC). PCMCIA (Personal Computer Memory Card Interface Association) and JEIDA (Japan Electronic Industry Development Association) have taken the initiative in prescribing mechanical and electrical specifications of PC cards. These specifications are hereby incorporated by reference. At present various kinds of PC cards are on the market, including memory cards, flash memory cards, HDD cards, and FAX/MODEM cards.
These PC cards are classified into 8-bit PC cards, 16-bit PC cards, and 32-bit PC cards, according to the width of an internal data bus. Currently marketed PCs have PC card slots provided therein for accepting various types of PC cards. However, PC card slots formed in some conventional PCs accept only a 16-bit PC card and a 32-bit PC card cannot be inserted into such a slot.
According to the above-mentioned specifications, a projection is provided in the vicinity of a PC card slot in order to identify the type of a PC card to be inserted into the slot. In this connection, a PC card has a groove formed therein in the vicinity of a connector thereof in order to receive the projection. The groove is sufficiently deep to accept the projection. The specifications dictate that a projection provided in a PC card slot dedicated to a 16-bit PC card be higher than that provided in a PC card slot dedicated to a 32-bit PC card. Accordingly, when a user attempts to insert a 32-bit PC card into a PC card slot dedicated to a 16-bit PC card, a projection provided in the slot prevents the insertion because the corresponding groove formed in the 32-bit PC card is too shallow to receive the projection. Since a drive voltage for a 32-bit PC card is 3.3 V, whereas that for a 16-bit PC card is 5 V, such a structural feature is appropriate for protecting an internal circuit of a card.
As the functions of PCs improve, the bus width of a PC card generally shifts from 8 bits to 16 bits and 32 bits. Currently released PC cards are most commonly of the 32 bit variety. However, many users still use PCs having a PC card slot dedicated to only a 16-bit PC card. According, if newly manufactured PC cards are adapted to operate in both 32-bit and 16-bit operation modes, they will be accepted by many more users.
However, because of the above-mentioned specifications, a 32-bit PC card cannot be inserted into a slot dedicated to a 16-bit PC card. Even when a groove formed in a 32-bit PC card is made deeper so that the 32-bit PC card can be inserted into a 16-bit PC card slot, neither the 32-bit PC card nor the associated PC can identify the 32-bit PC operation mode; thus, the 32-bit PC card cannot be operated properly.